The aim of this research proposal is to investigate three aspects of an experimental colonic carcinoma; (1) the immunological status of the laboratory colon cancer bearing host; (2) the treatment by immunotherapy of the laboratory animal with lymph node-positive colonic carcinoma; and (3) the evaluation of therapeutic modalities other than radical operation in the primary treatment of rectal carcinoma. Carcinomas of the colon in the rat have been established with the carcinogen 1,2-dimethylhydrazine. The primary tumors were transplanted to the subcutaneous space and will be exteriorized to the colons of syngeneic hosts. Immunological status will be evaluated by the in vitro correlates of cell-mediated immunity, using microcytotoxicity assays. Immunospecific regression of established subcutaneous and colonically re-implanted carcinomas will be attempted using tumor cells, tumor cell membranes or soluble antigen modified by neuraminidase, Concanavalin A, iodoacetamide, or by lipid-conjugation. Non-specific immunotherapy with BCG in both models of the established tumors will also be evaluated. Specific emphasis will be placed on the role of adjuvant immunotherapy in the lymph-node-positive host following conventional excision of the intestinally re-implanted tumor. The in vitro assays of cell-mediated immunity will be repeated in the animals undergoing all forms of therapy. Recent advocates of electrocoagulation for rectal carcinoma cite the fact that the 55% five-year survival following radical resection has not improved in two decades. These authors have proposed that electrocoagulation for rectal carcinoma replace the abdomino-perineal resection as the primary mode of therapy without benefit of prospective clinical analysis or experimental study. This syngeneic model will be employed to evaluate the role of electrocoagulation in the primary therapy of adenocarcinoma of the colon. Clinical studies of electrocoagulation as primary therapy are not amenable to pathological staging. In contrast, this experimental system is purposely designed to render intestinal and mesenteric lymph node specimens suitable for the study of the effect of primary tumor electrocoagulation on tumor- positive lymph nodes. Simultaneous in vitro testing may corroborate a role for the immune system.